Institute at Brown for Environment and SocietyIBES

Graduate Students: Earth, Environmental & Planetary Sciences

Abigail's general interests concern how turbulence and forced mixing affect atmospheric and ocean dynamics. She uses mostly theory and models to study the interaction between these smaller scale processes and the larger scale dynamics. In her PhD studies, Abigail is focused on better understanding the effects turbulence has on ocean fronts, which play an important role in transporting carbon and other tracers from the ocean surface into the interior, as well as supplying essential nutrients to marine biology. Prior to Brown, Abigail worked on her Masters degree at Tel Aviv University, where she studied extreme events in the atmospheric global circulation in the presence of topography. 

Cheung is interested to understand how climate has varied and changed throughout the mid-late Holocene and the past two millennia. At Brown, he is using biomarkers in sediment cores to reconstruct decadal to centennial climate variability in the Pacific. He is also interested in using climate models to understand the dynamics and mechanisms of driving variations in the Pacific.

Sydney studies the reactive nitrogen cycle in changing cryosphere environments using stable isotopes of nitrogen and oxygen to study the intersection between atmospheric chemistry, deposition and biogeochemistry. Her current work is focused in the Colorado alpine where lake water chemistry is heavily influenced by atmospheric pollution, glacial melt and biological processes. However, air pollution mitigation implemented by the Clean Air Act suggest that atmospheric nitrogen deposition plays a much smaller role in driving ecosystem biogeochemical changes, so why are background levels of inorganic nitrogen species so high in these lakes and what mechanisms are driving these nutrient levels? This work has implications for ecosystem health and environmental change, but also human health as these high alpine snow-fed lakes are critical sources of drinking water for local communities.

Sarah uses satellite remote sensing to study Arctic lakes and rivers to better understand how the Arctic hydrologic system is responding to climate change. She is particularly interested in broad-scale patterns in Arctic terrestrial hydrology and the development of new remote sensing techniques for studying hydrologic change. Her current project involves analyzing seasonal lake dynamism using CubeSat satellite imagery across the North American high latitudes.

Sloane studies organic geochemical proxies found in eastern African lake sediment cores to reconstruct past variability in precipitation and temperature in this region since the Last Glacial Maximum. She is currently working on generating a precipitation record from Lake Rutundu, Mt. Kenya, and plans to compare this data to existing hydroclimate records from eastern Africa to better understand the hydroclimate history and atmospheric processes controlling rainfall in this region.  She also hopes to use her research to understand how precipitation and temperature will change in the future and the impact these changes will have on the ecology, cultural practices, and economy associated with natural environments in eastern Africa.  

Sarabeth has a background in geology and oceanography, and is now a part of the Brown-Marine Biological Laboratory joint program. Her past research focused on bacterially-mediated iron oxidation and the bioavailability of biogenic iron oxides to iron-limited marine phytoplankton communities. For her PhD, she will integrate organic geochemistry and bioinformatics to investigate how lipid biomarkers respond to and record shifts in environmental variables. 

Emily is interested in the relationship between atmospheric deposition and nitrogen biogeochemistry in urban, coastal environments. The goal of her research is to identify atmospheric deposition impacts on Narragansett Bay by characterizing the isotopic composition of local nitrogen sources. Narragansett Bay extends a gradient of sources (including: the city of Providence, industrial plants, golf courses, wastewater treatment plants, and a major airport); as a result, the bay is impacted immensely by urban deposition, resulting in poor water quality. Emily seeks to: 1) quantify how much nitrogen is entering the bay through atmospheric deposition and in what form, and 2) use isotopic signatures to trace sources to understand the biogeochemical impacts on local ecosystems.

Jennifer is interested in how plants respond to and affect the climate.  For her master's thesis at Wesleyan University, she measured the composition and morphology of fossil leaves to estimate the level of carbon dioxide in the atmosphere millions of years ago.  At Brown, she plans to investigate feedbacks between vegetation, hydrology, and climate.

Ethan Kyzivat uses remote sensing observations to study surface hydrology. In particular, he is interested in hydrologic change in arctic areas, including from anthropogenic climate change. This past summer, he participated in a month-long field trip in northern Alberta, taking river measurements as part of a satellite calibration team. He plans to use this data to study hydraulic geometry and water classification from imagery.

Rachel continues to study the paleohydrology and paleovegetation of East Africa and how that relates to the evolution of our hominin ancestors. By using lake sediment drill cores, she analyzes organic compounds to understand how the environment changed through time and drove hominins to speciate, go extinct, and disperse out of Africa. As a 5th year graduate student, Rachel is compiling her work to create syntheses of many records to get a broad view of East African paleoclimate over the past few million years.

Sarah is a Ph.D. graduate student in the Department of Earth, Environmental, and Planetary Sciences, conducting paleoclimate and paleoceanography research. She works on paleoclimate reconstructions to understand past and future climate dynamics. Sarah is currently studying sediment cores from the Bay of Bengal using multiproxy techniques to understand Indian Summer Monsoon dynamics and mechanisms. It is important to understand the Indian Monsoon system response to climate changes since over half of the world’s population lives in the Indo-Asian monsoon region depending upon monsoonal rains for water and agriculture.

A variety of means exist by which earth scientists study environmental change on geologic timescales; in particular, organic molecules preserved in ocean and lake sediments can be used to reconstruct the histories of monsoons, El Niño, and other massive weather events on thousand- to million-year timescales. Constraining the past meteorological changes that occur in response to deglaciation, insolation, and rising levels of greenhouse gases helps climate modelers project trends into the near future as anthropogenic warming continues. In turn, better-informed models and predictions have the potential to characterize particularly high-risk regions and thus ameliorate the impacts of weather-driven, climate-ampli ed natural disasters.

Ashling works on reconstructing precipitation and evaporation using biomarkers preserved in lake sediments. Currently this is being applied to Lake Tanganyika in East Africa to reconstruct hydroclimate since the last glacial maximum.

Jenna's research centers on using use statistical methods to gain information about upper ocean characteristics in coastal oceans. Dispersion and velocity variance inform models about bulk surface statistics and are relevant to oil prediction capabilities.

Nora studies organic geochemical and molecular biomarkers in lake sediments to develop climatic and ecological reconstructions over time. Her current research focuses on multi-decadal and centennial climate changes in the North Atlantic over the past 2,000 years using lake sediment records from Iceland and the Azores to refine our understanding of the natural processes (i.e., the Atlantic Multi-Decadal Variability) governing climate fluctuations. In addition, Nora is interested in understanding how human settlement in Iceland and the Azores has contributed to major environmental changes.

Aakash is studying physical oceanography in the Fox-Kemper Lab. His research aims to measure the capabilities of forecasting models, in particular the computational climate model used to forecast Narragansett Bay. His general research interests are fluid dynamics and geophysical flows.

Keith Spangler studies how climate change affects human health and well-being. His research seeks to quantify how the cumulative health risks of climate change vary spatially as functions of multiple climatic hazards and social vulnerabilities. This work is motivated by a desire to inform public health interventions aimed at improving population health and resilience to climate change at various spatial scales.

Richard Vachula uses paleoecological and organic geochemical techniques to reconstruct terrestrial environmental histories (including climate, ecology, and anthropology) from lake sediment archives. His research has focused upon topics including the interplay between cultural perceptions of climate change and the Arctic, the Holocene climatic history of Alaska’s North Slope, and computational modelling of lake sediment-based fire history proxies. He is particularly interested in the dynamic interactions between fire, climate, ecology, and human land use.

Karen's main research interest is on alkenone-based paleoclimate proxy. By applying multi-disciplinary approaches from DNA sequencing to gas chromatography, Karen has gained valuable information about the alkenone producing haptophyte community. That information will greatly improve our ability to decipher temperature and salinity signals in sediment record in sites such as Chesapeake Bay.

Mengxi is interested in the land-atmosphere interaction from the perspective of energy and hydrology. Over the past two years at Brown, he studied the empirical relationship between atmospheric energetics and convective strength in the tropics using satellite data. He is currently working on computer simulation of moist convection in a tropical rainforest, which is an extension of his previous project.

Weixuan's research interest is to study the formation of Asian monsoons and the mechanisms that might affect their wind and precipitation. She is using modeing skills that estimate how the East Asian monsoon is different from the Indian monsoon, and what contributes to these differences.

Xiangming uses biogeochemical/geochemical indexes (alkenone unsaturation index U­­­k'37, hydrogen isotope ratio ẟD) to study the past variations of sea surface temperature (SST) and sea surface salinity (SSS). SST and SSS are very important in disclosing the warm and cold climate history of the Earth and therefore, provide necessary benchmarks for predicting future climate change. He is recently working on constructing a global map of ocean surface temperature using U­­­k'37paleotemperature index for MIS M2 event (~3.2 million years ago), to search for the possible causes of this special cooling event. 

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